1. Technical Field
The present invention relates to an image processing device, a projection display device, and an image processing method.
2. Related Art
In the past, there have been used a projector as a projection device of an enlarged image used for image viewing in, for example, presentations in exhibitions, academic conferences, meetings, and so on, and home theaters.
Generally, the screen used as a projection target surface of a projector, in the case of a reflective screen, for example, reflects the projection light from the projector to thereby display the projection image, and at the same time, reflects the outside light derived from the use environment such as illumination light or sunlight entering from a window. Therefore, there arises a problem that if the projector is used in a bright place, the contrast as a luminance ratio between “white (the highest luminance)” and “black (the lowest luminance)” is lowered to thereby make clear image display difficult.
In order for solving this problem, development of a screen aimed to realize an improved contrast in bright rooms by suppressing the influence of the outside light causing the degradation in the contrast such as sunlight or illumination light to thereby lower the minimum luminance is in progress. As such a screen there is proposed a screen having a configuration in which a light absorption layer including dye or a pigment for absorbing light is provided to thereby absorb unwanted outside light (see, e.g., JP-A-2002-107828 (Document 1)).
Incidentally, although projectors have an advantage of being capable of displaying projection images on various types of projection target surfaces such as screens or walls, the colors of the projection image vary between the projection target surfaces in accordance with the surface conditions of the projection target surface including the color, the depth of the color, and roughness of the surface, and the vision felt by the observer also varies.
For example, the vision is different between the projection image obtained by performing the projection display on a white screen from the projector and the projection image obtained by performing the projection display on a blackboard installed in a classroom of a school. Further, there also arises a problem that if the image display is performed under the illumination light (the outside light) after adjusting the colors of the projection image in a darkroom, the colors are shifted from the setting to thereby degrade the color reproducibility.
In order for solving this problem, there has been proposed a configuration of a projector in which the color information of the projection image on the screen is measured using a color information sensor, and the correction is performed so that the projection image has desired colors and illuminance based on the measurement value (see, e.g., JP-A-2008-165231 (Document 2)).
However, the following problems exist in the inventions described in the documents mentioned above. The screen which absorbs the light with a specific wavelength described in Document 1 can be used as an achromatic screen which preferably absorbs the light of a fluorescent lamp to thereby reduce the influence of the outside light if, for example, it is designed assuming that the fluorescent lamp as the outside light.
However, considering the case in which the screen on which such a design in performed is used in the outside light (e.g., white LED illumination) different from the fluorescent lamp, since the distribution (spectral characteristics) of the light components included in the outside light is different between the types of the outside light, coloring is caused by the outside light obtained after absorbing the light with the specific wavelength, and as a result, it is possible that the achromatic screen fails to be obtained.
In such a case, it is possible to correct the color shift using the invention described in Document 2 having the problem of solving the color shift in the projection image under the presence of the outside light similarly to the case of Document 1. However, in the invention according to Document 2, in order for the correction, it is required to measure the coloration of the screen after absorption of the outside light using the color information sensor, and then determine the correction value based on the measurement result.
In order for making such correction possible, it becomes necessary to perform spectrographic measurement such that what wavelength the light strongly reflected by the screen on which the image projection is not performed has, and what wavelength the light not so strongly reflected by the screen has, and thus the coloration is caused. However, the color information sensor for making such measurement possible is extremely expensive, and is therefore not realistically adopted in the projector used for a general purpose. Further, in the case of using a sensor with low accuracy, a preferable color correction is not achieved, and the intended correction of the color shift is not achieved.